In cell culturing, troublesome passaging processes such as exchange of culture media in incubators and reseeding for attaining proper cell density are carried out by hand operations. In order to avoid occurrence of contamination, usually, these operations are carefully carried out in a relatively clean atmosphere controlled in concentration of floating dusts in the air by the technology for formation of clean environment which has been cultivated in the field of production of semiconductors. However, this clean atmosphere is still insufficient for avoiding contamination, and in the case of culturing cells in a circular laboratory dish (Schale) ordinarily used as an incubator, exchange of culture media is carried out by quickly inserting a pipette between the dish and its lid with holding up the cover, taking care that bacteria are not incorporated and that the pipette does not contact with circumferential matters such as edge of the dish. Such operations are frequently and always carried out by highly skilled workers.
[Patent Document 1] U.S. Pat. No. 5,985,653